Paleoclimatic evolution of Southwestern Gondwana during the Late Paleozoic: a record from ice-house to green-house conditions

LIMARINO, C.O.; SPALLETTI, L.A.; ISBELL, J.; CÉSARI, S.; GEUNA, S.E.

Perth

Congreso; XVII International Congress on the Carboniferous and Permian; 2011

The complex paleoclimatic history of the late Paleozoic has captured the attention of geologists since the end of the XIX century when glacial deposits were reported from distant areas of Gondwana. However, other paleoclimatic conditions also hold a far deeper influence on Carboniferous and Permian stratigraphy. Indeed, the late Paleozoic is unique in Earth history in that a long-term transition from icehouse to greenhouse conditions was preserved on a global-scale. In this paper we divide the stratigraphic record of the icehouse-greenhouse transition in South America into four major stages: 1. Late Visean-Early Bashkirian (icehouse), 2. Late Bashkirian-Early Cisuralian (terminal icehouse) 3. Late Cisuralian-Guadalupian (transition from humid to semiarid conditions) and 4. Lopingian (greenhouse). The Late Visean-Early Bashkirian (icehouse, stage 1) is well recorded along the western margin of Gondwana in Argentina (Guandacol, Hoyada Verde and Agua de Jagüel Formations), Bolivia (Tupambi Formation) and Brazil (Poti Formation). Radiometric U/Pb ages indicate that the glacial event ended in the Andean region not later than 319.57 Ma (Late Serpukhovian). To the east, glacial conditions persisted in the Paraná and Tarija basins until the Late Pennsylvanian. The end of glaciation across most of South America took place during the Late Bashkirian-Early Cisuralian (stage 2). Glacial diamictites were covered by transgressive shales in the Itararé Group (Lagoa Azul Formation, Brazil), Lower San Gregorio Formation (Uruguay) and Tupambi Formation (Bolivia and Argentina). In the Andean region, coal-bearing fluvial deposits containing the NBG fossil flora prevailed. Climatic conditions were markedly different in the western (Andean) and eastern (pericratonic) South American basins from the Late Cisuralian to the Guadalupian (stage 3). These differences likely resulted from initiation of Choiyoi volcanism in the Andean region, which influenced local- and regional-scale climactic conditions. While eolian deposits, alternating with fluvial red beds and playa lake successions, appeared in the western Andean basins (Patquía and De La Cuesta Formations), fluvial and estuarine coal beds occurred in the Paraná Basin (Lower part of the Río Bonito Formation). Finally, extremely arid greenhouse conditions(stage 4),dominated during the Lopingian when thick red bed-bearing ephemeral river, evaporite, and eolian successions were deposited in various places in South America (Talampaya, Chutani, Vitiacua  Formations).